Hi Steve,
At the RV Park we stayed in last weekend their was a 3075RLF. The owner said that they bought it off of a Dealer lot in October and this was their first trip in it. I took a quick look in his 3075 and he looked in mine but, the only obvious differences we could see was, we had different color interiors and I had the LCD television and he didn't.
The 3075RLF on the dealer lot looked new so, I don't think it would have been built before November when my unit was built.
I guess for now the mystery remains.